With conventional printing methods having become the printing screen is forced with adjustable pressure onto the surface of the substrate to be imprinted. However, the printing screens and the bed are in a fixed relation to each other, i.e., the distance between the two elements is constant. In case the thickness of the substrate changes, it is necessary to readjust this distance. Systems are known in which the printing screen is so mounted as to rest almost with no pressure on the substrate to be imprinted.
When printing relatively thick, i.e. highly piled substrates, very large frictional forces are exerted by the substrate onto the printing screen on account of the compression of the substrate. These forces are generated by bending the pile threads which are rather stiff and extend vertically in the most cases. These threads tend to become jammed in the perforations of the printing screen and, on being deflected against the direction of motion during the printing process, subject the screen wall to great stress.